# Dynamics of strongly coupled disordered dissipative spin-boson systems

## TL;DR

This paper explores the complex dynamics of strongly coupled, disordered, dissipative spin-boson systems, revealing thermalization, out-of-equilibrium behavior, and potential for cooling, with implications for quantum energy landscape engineering.

## Contribution

It demonstrates that a spin Hamiltonian description remains valid in strong coupling and dissipation regimes, enabling new insights into their many-body dynamics.

## Key findings

- Identification of approximately thermal regimes in dissipative strong coupling
- Discovery of out-of-equilibrium dynamics breaking detailed balance
- Potential for cooling spin degrees of freedom under specific conditions

## Abstract

Spin-boson Hamiltonians are an effective description for numerous quantum many-body systems such as atoms coupled to cavity modes, quantum electrodynamics in circuits and trapped ion systems. While reaching the limit of strong coupling is possible in current experiments, the understanding of the physics in this parameter regime remains a challenge, especially when disorder and dissipation are taken into account. Here we investigate a regime where the many-body spin dynamics can be related to a Ising energy function defined in terms of the spin-boson couplings. While in the coherent weak coupling regime it is known that an effective description in terms of spin Hamiltonian is possible, we show that a similar viewpoint can be adopted in the presence of dissipation and strong couplings. The resulting many-body dynamics features approximately thermal regimes, separated by out-of-equilibrium ones in which detailed balance is broken. Moreover, we show that under appropriately chosen conditions one can even achieve cooling of the spin degrees of freedom. This points towards the possibility of using strongly coupled dissipative spin-boson systems for engineering complex energy landscapes together with an appropriate cooling dynamics.